"The human mind shows an urge to capture into fixed forms through unreal assumptions, that is, fictions, that which is chaotic, always in flux, and incomprehensible. Serving this urge, the child quite generally uses a scheme in order to act and to find his way. We proceed much the same when we divide the earth by meridians and parallels, for only thus do we obtain fixed points which we can bring into a relationship with one another."